1. Field of the Invention
The invention relates to a lens suction jig installing apparatus and a method of determining a lens position using the apparatus thereof, and in particular to an improvement thereof in determining a lens position when installing a lens suction jig to a progressive multi-focal lens.
2. Description of the Related Art
A raw spectacle lens having an approximately spherical surface cutout shape with a predetermined size has been provided these days. The raw spectacle lens is edged to have a shape that fits with a shape of an eyeglass frame.
Edging process for the raw eyeglass lenses is performed by an edging process apparatus. Because the processing by the edging process apparatus is conducted with a processing center of the lens as a reference, the processing center of the lens is obtained beforehand prior to the processing. A lens suction cup (a lens suction jig) is installed at the processing center, which is carried out by a lens suction jig installing apparatus.
By the way, the spectacle lens contains some types such as a single focal lens, a bifocal lens (multi-focal lens), and a progressive multi-focal lens. The processing center of the single focal lens is an optical center thereof. The processing center of the multi-focal lens and progressive multi-focal lens is their respective eye-point positions (EP values).
The optical center of the single focal lens can be obtained relatively easily using a lens meter. On the other hand, the eye-point position for each of the multi-focal lens and the progressive multi-focal lens is specified, with an appropriate index formed beforehand for their respective raw lenses as a reference.
For example, the multi-focal lens has a near portion segment formed, and the eye-point position thereof is set, with a contour of the segment as a reference. On the other hand, since the progressive multi-focal lens does not have a segment formed as the multi-focal lens does, no distinction can be made between a near portion and a far portion of the lens at a first sight. Accordingly, since the progressive multi-focal lens has a line (a second index) for indicating a boundary between the near portion and the far portion and a symbol such as “+”, printed on the surface of the lens, for showing the far portion, the eye-point position can be found regarding the line as a reference.
The printed second index is not represented in a step where a raw lens is manufactured by, for example, a cast, but is added after the shape is formed.
That is, more than two indices (first indices) called concave or convex hidden marks are formed on the surface of a raw progressive multi-focal lens during a step of forming a shape, and the second index is printed based on the first indices after forming a shape.
The first indices include, for example, two marks that stipulate a boundary line between the near portion and the distant portion as described above. However, there is a case in which, in addition to the marks, letters and symbols such as figures representing a difference in refracting power between the near portion and the distant portion are added.
The letters additionally formed may be used to distinguish left from right by the fact that the position of the letters for the left eye lens is made different from that for the right eye lens. It is natural that even if letters are not additionally provided, a distinction between left and right can be easily made by making the two marks themselves mutually different.
The conventional lens suction jig installing apparatus holds a spectacle lens having the first index and the second index described above on a position adjustable pedestal. Making an image capture device capture the spectacle lens, an image obtained as the spectacle lens is displayed on the display. At the same time, the image obtained as the spectacle lens is graphically processed to detect the first and second indices. Based on the detected first and second indices, an installing position of the lens suction cup (processing position) is obtained, and the lens suction cup is sucked at the installing position. See, for example, Japanese Patent Publication 2000-19058 and Japanese Patent Publication 2002-26083.
As shown in FIG. 50, paint marks (printed marks) such as a horizontal line HL in progressive multi-focal lens, a cross mark Ma, a distant position display mark Mf, a near position display mark Mn, a hidden mark Hm, and an approximate suction position are different depending on lens manufacturers or types of lens. In addition, manufacturing errors are not precisely in print.
For example, the paint mark (printed mark) such as a mark representing an approximate suction position is marked at predetermined positions such as 0.00 mm, 2.0 mm, and 4,0 mm (in FIG. 50, X2=approximately 4.0 mm). In reality, the paint mark is drawn at a position X1 off he predetermined position X2. It is a well-known fact in the spectacle processing industry that the paint mark is marked at the wrong position X1.
Accordingly, when a suction jig is installed based on these marks, an error is piled up, which prevents correct suction work. If lens cutting process is performed according to the suction position, it is possible that incorrect lens processing is conducted.
If the types of lens can be determined regarding these marks, a manual by a lens manufacturer shows that predetermined values such as 0.0 mm, 2.0 mm and 4.0 mm are indicated, which can specify suction positions. However, reading a manual every time reduces working efficiency, which prevents speedy suction work and lens grinding process.